[libvirt] [PATCH 3/3] qemu: use job to keep driver responsive on qemuDomainOpenChannel

[Nikolay Shirokovskiy]

As we now assume that virChrdevOpen can take a significant time
we should take a job and drop vm lock during operation to keep
qemu driver responsive.

We drop vm lock but access vm structures after it because we are
in exlusive modify job so vm structures can only be read concurrently.
---
 src/qemu/qemu_driver.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 6132bc4..9401695 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -16386,6 +16386,8 @@ qemuDomainOpenChannel(virDomainPtr dom,
     size_t i;
     virDomainChrDefPtr chr = NULL;
     qemuDomainObjPrivatePtr priv;
+    virQEMUDriverPtr driver = dom->conn->privateData;
+    bool job = false;
 
     virCheckFlags(VIR_DOMAIN_CHANNEL_FORCE, -1);
 
@@ -16395,6 +16397,10 @@ qemuDomainOpenChannel(virDomainPtr dom,
     if (virDomainOpenChannelEnsureACL(dom->conn, vm->def) < 0)
         goto cleanup;
 
+    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
+        goto cleanup;
+    job = true;
+
     if (!virDomainObjIsActive(vm)) {
         virReportError(VIR_ERR_OPERATION_INVALID,
                        "%s", _("domain is not running"));
@@ -16432,11 +16438,13 @@ qemuDomainOpenChannel(virDomainPtr dom,
         goto cleanup;
     }
 
+    virObjectUnlock(vm);
     /* handle mutually exclusive access to channel devices */
     ret = virChrdevOpen(priv->devs,
                         chr->source,
                         st,
                         (flags & VIR_DOMAIN_CHANNEL_FORCE) != 0);
+    virObjectLock(vm);
 
     if (ret == 1) {
         virReportError(VIR_ERR_OPERATION_FAILED, "%s",
@@ -16445,6 +16453,9 @@ qemuDomainOpenChannel(virDomainPtr dom,
     }
 
  cleanup:
+    if (job)
+        qemuDomainObjEndJob(driver, vm);
+
     virDomainObjEndAPI(&vm);
     return ret;
 }
-- 
1.8.3.1